Question: A bag contains $11$ red marbles, $7$ green marbles, and $8$ blue marbles. If a marble is randomly chosen, what is the probability that it is not blue?
Solution: There are $11 + 7 + 8 = 26$ marbles in the bag. There are $8$ blue marbles. That means $26 - 8 = 18$ are not blue. The probability is $ \frac{18}{26} = \dfrac{9}{13}$.